Many HIV prevention programs have been demonstrated efficacious for youth, yet the effects are often not maintained over the long term (e.g., Rotheram-Borus et al. 1995). Street Smart (SS) is an effective HIV preventive intervention for homeless youth (Rotheram-Borus, et al., 1991) selected by the CDC as part of Replicating Effective Programs (2000). However, substantial relapse diminishes the program's effects over two years. This proposal aims to examine interpersonal & computerized strategies for maintaining the efficacy of the SS intervention for 400 homeless youth in Los Angles (LA). A two-stage sampling strategy (agency level & then youth within agency) is planned to conduct a randomized controlled trial examining the efficacy & cost-effectiveness of SS for reducing risk for HIV among homeless youth aged 12-20 years in four conditions: 1) SS, but no maintenance strategy (SS; n=100); 2) SS & an interpersonal strategy for behavioral maintenance (Interpersonal SS; n=100); 3) SS & a computerized internet-based strategy for behavioral maintenance (Computerized SS; n=100); & 4) a one-session AIDS video Control Condition (CC; n=100). Based on a social learning theory (Marlatt, 2000), each maintenance strategy will provide skill training, social support, informational updates, & access to an expert for consultation, referrals, & coping with emerging crises. Shelter staff will deliver all interventions to ensure replicability & youth's utilization of maintenance programs will be documented. Youth will be assessed at recruitment, & at 3-, 6-, 12-, 18-, & 24 month intervals in three domains: 1) youth's substance use & sexual behaviors; 2) youth's & staff members perceptions of the program's acceptability & quality & program utilization over time; & 3) the generalization of the program's effects on youth's problem behaviors (sex work, delinquent acts, conduct problems, school truancy/unemployment, emotional distress, & chronic homelessness). If positive intervention effects are being maintained for two years, we will apply for an extended follow-up of the project in order to monitor youth for up to five years following intervention delivery.